This is because wet mortar has moisture. So if you grout your tiles too soon, you end up trapping the moisture from the mortar, which can lead to mold and other problems.
There is no reason not to wait to apply grout, unless you have used a quick-set tile adhesive. The thin-set mortar needs time and air to properly set and cure for strong bonding. Improper curing can lead to a flaky adhesive, which will cause loose or failing tiles and bonds.
Grout is used to fill the gaps between walls, usually tiles, so that they stick together. For grout to work its magic, it should be left to dry for a reasonable amount of time; otherwise, all your efforts will be ruined. On average, grout takes around 24-72 hours to dry.
Applying sealer too early can trap moisture, leading to potential damage or a weakened seal, so ensuring the grout is fully dry is pivotal.
The grout can dry out as well as not seal which will allow water under it which in turn can cause damage to everything making up the floor including the tile and any other material (wood, the structure of the building) under it. Water causes damage to the structure of a building.
However, a common guideline is to wait approximately 15 to 30 minutes after applying the grout before wiping off the excess. This initial waiting period allows the grout to firm up and achieve a workable consistency.
However, if your tiles look cloudy or hazy after installation, it is likely a result of grout haze. It may take grout haze a few days to reveal itself, but it should be removed as soon as possible after the grout has dried completely (wait at least 24 hours).
Grout Must Set and Cure
Then the grout needs to be cured for a couple of days. That usually takes between 48 and 72 hours. If you can avoid walking on your floor for that amount of time, that would be ideal.
Step 1: Make sure the grout is dry.
All new grout should be allowed to cure fully before being sealed. Even if the grout appears to be hard, achieving the correct color will require time for excess moisture to evaporate.
You can apply new grout right over the top of the old grout. To do this, all you need is a grout removal tool. Use the tool to strike out the old grout, making sure the depth is at least 2mm, which is about the thickness of two dimes stacked one on top of the other.
Start by combining four parts water and one part white vinegar (hint: add more vinegar to increase the cleaner's strength). Pour into a bucket or spray bottle and apply the water and vinegar mixture to the tile surface. Scrub the area using a cloth, nylon pad, or a mop.
While the initial drying process may take several hours, the curing process can span days, weeks, or even months, depending on various factors. It's not uncommon for grout to achieve its maximum strength potential only after 28 days of continuous curing under ideal conditions.
The typical cement ground found at most hardware stores takes 48 to 72 hours to dry. It's tempting to touch grout to see if it's dry, but try to resist. That said, you'll likely notice that wet grout is much darker than dry.
And, like sanded grout, unsanded grout typically takes up to a full 72 hours to cure. You'll also need to apply a penetrating sealer when using unsanded grout in a bathroom. Epoxy grout, made by combining a hardener with epoxy resin, takes just 24 hours to cure.
It is recommended to wait 3 days before using the shower.
What happens if grout gets wet before it cures? If you start exposing grout to water before it has properly dried it can lead to a few issues that you don't want to be dealing with. Typically it will weaken the grout and eventually it will start to crumble and even fall out.
When you grout too soon, you may end up with damaged tiles, especially cracked tiles. Not only do cracks look unsightly, they can also allow water to seep underneath the tiles, potentially resulting in mold and water damage.
It is important not to leave any excess sealer on the tile surface because it won't get absorbed and it can leave a sticky surface that can become a maintenance problem.
Allow the grout to dry completely overnight. Use a dry cloth to buff away any remaining haze on the tile surface. Don't use a wet cloth or sponge, or you may moisten the grout and disturb its curing. Over the next 24 to 72 hours, avoid walking in the space to protect the newly applied grout.
Porous grouts attract water, dirt, oils, etc. While the tile industry does not require sealing, it is always recommended, especially in wet or high-traffic areas. Penetrating sealers are the most commonly used and offer high water, chemical and stain resistance.
A good rule of thumb is to clean as you go, working in small sections. This is especially important if the grout application is slow-going. Optimally, no more than 30 minutes should pass for the initial wiping off of excess grout.
Humidity Levels
Humidity just refers to how much moisture is circulating in the air. That moisture level will impact how quickly tile dries, of course. High humidity means slower drying times and low humidity makes for quicker drying times.
Once you've activated the micro-scrubbers inside, your Magic Eraser is good to go. Start by swiping it firmly across the desired surface. In just a few swipes, you should start to see grout messes and buildup begin to disappear!
Topical sealers (acrylic sealers) which coat the grout joint and are not vapor permeable may turn white from reactions between the acrylic and moisture. This is not efflorescence. Rather this is similar to the whitish haze seen with floor wax when it is applied to a damp surface.
Generally, you should be okay to mix up some grout and touch up any trouble spots in your new grout. Stuff like pin holes, scratches or low spots can be touched up with fresh grout the next day. The trick is to blend in the new grout with the old so make sure you mix it the same way that you mixed it the day before.